Low birth weight (LBW) related to preterm birth of newborns is the leading cause of infant mortality in the United States. Its incidence, which has not decreased in the last twenty years, varies by ethnicity. Stress, anxiety, and depression are potential major factors in ethnic differences in preterm birth. Hispanics are one of the fastest growing ethnic groups in the US, having a pronounced increase in the preterm birth rate associated with length of stay in the US. At the same time there is a paucity of studies with biological components that examine the problem of prematurity and LBW in Hispanics. The overall purpose of this proposal is to test a biobehavioral model of causal pathways initiated by stress, cervical changes, and depression that may alter endocrine and immune factors leading to an inflammatory response, cervical changes, and ultimately LBW and preterm birth in Hispanics. The specific aims are to 1) determine the effects of stress, anxiety, and depression on endocrine and immune factors in Hispanic pregnant women that may lead to an inflammatory response and cervical changes resulting in alterations in gestational age at birth and birth weight, 2) assess the effects of stress, anxiety, and depression on health behaviors in pregnant Hispanic women that may impact endocrine and immune factors resulting in alterations in gestational age at birth and birth weight, and 3) ascertain the effects of demographic factors, social/cultural factors, and previous preterm birth on stress, anxiety, and depression in pregnant Hispanic women. In this prospective study pregnant women (n=508 minimum) will be recruited from two sites. Blood samples for assessment of levels of hormones, cytokines, and neopterin will be taken. Vaginal samples for assessment of levels of cytokines, neopterin, fetal fibronectin and bacterial vaginosis will also be obtained. Psychological questionnaires assessing stress, anxiety, and depression will be completed. Cervical length will be assessed by vaginal ultrasound. Medical record review for neonatal outcome data and an assessment of gestational age and birth weight will be completed after delivery on infants greater than 35 weeks. Data analysis will include structural equation modeling, multiple linear and logistic regression analysis, and correlation coefficient analysis. There is an urgent need to better understand the determinants of ethnic disparities as well as pathways involved in preterm birth. This study adopts a dynamic, biobehavioral approach that holds great promise in understanding the problem of preterm birth in Hispanic women. A clearer understanding of the interrelationships of the pathways leading to preterm birth and associated LBW is essential to determine and develop appropriate preventive strategies.